Department of Applied Chemistry, Faculty of Engineering, Hiroshima University, Higashi-Hiroshima 739-8527, Japan.
Inorg Chem. 2011 Jul 4;50(13):6372-7. doi: 10.1021/ic200826d. Epub 2011 Jun 6.
A new binary barium germanide BaGe(3) was prepared by high-pressure and high-temperature reactions using a Kawai type multi-anvil press. It crystallizes in a hexagonal unit cell with a = 6.814(1) Å, c = 5.027(8) Å, and V = 202.2(5) Å(3) (the space group P6(3)/mmc, No. 194). The unit cell contains two layers along the c axis composed of Ba atoms and Ge(3) triangular units. The triangular units stack along the c axis to form 1D columns in which the adjacent Ge(3) units turn to opposite directions. The columns, therefore, can be described as the face-sharing stacking of elongated Ge(6) octahedra. Each Ba atom is surrounded by six columns. BaGe(3) is metallic and shows superconductivity at 4.0 K. The band structure calculations revealed that there are four conduction bands mainly composed of Ge 4p and Ba 5d orbitals. From Fermi surface analysis, we confirmed that three of them have a large contribution of Ge 4pz orbitals in the vicinity of the Fermi level and show a simple 1D appearance. The remaining one contains Ge 4px, 4py, and Ba 5d contributions and shows a 2D property.
一种新的二元钡锗化物 BaGe(3) 通过使用 Kawai 型多砧压机的高压高温反应制备而成。它在六方晶胞中结晶，a = 6.814(1) Å，c = 5.027(8) Å，V = 202.2(5) Å(3)（空间群 P6(3)/mmc，No.194）。晶胞沿 c 轴包含两层，由 Ba 原子和 Ge(3)三角形单元组成。三角形单元沿 c 轴堆积形成一维柱，其中相邻的 Ge(3)单元转向相反方向。因此，这些柱可以描述为拉长的 Ge(6)八面体的共面堆积。每个 Ba 原子被六个柱包围。BaGe(3)是金属性的，在 4.0 K 时表现出超导性。能带结构计算表明，有四个主要由 Ge 4p 和 Ba 5d 轨道组成的导带。从费米面分析中，我们确认其中三个在费米能级附近具有 Ge 4pz 轨道的大贡献，并呈现出简单的一维外观。剩余的一个包含 Ge 4px、4py 和 Ba 5d 的贡献，并呈现出二维性质。
